| From: | Dimitri Fontaine <dfontaine(at)hi-media(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, daveg(at)sonic(dot)net, Andrew Dunstan <andrew(at)dunslane(dot)net>, Greg Stark <gsstark(at)mit(dot)edu>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Eliminating VACUUM FULL WAS: remove flatfiles.c |
| Date: | 2009-09-04 20:54:28 |
| Message-ID: | m2skf2zb0b.fsf@hi-media.com |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Dimitri Fontaine escribió:
>> Why can't MVCC apply here? You'd have two versions of the pg_class entry
>> that just has been CLUSTERed, and you keep the old relfilenode arround
>> too. MVCC applies, and you teach vacuum to clean out the old file when
>> cleaning out the no more visible tuple.
>
> It just doesn't work. pg_class (and various other rels) are special
> because they are needed to bootstrap the catalog system. See
> RelationCacheInitializePhase3. It wouldn't be possible to figure out
> what's pg_class relfilenode until you have read it from pg_class, which
> is precisely what we're trying to do.
Well at bootstrap time I guess noone is able to disturb the system by
placing a concurrent CLUSTER pg_class; call. Once started, do those rels
still need to have a special behavior?
I guess I'm being dense, will now let people in the know find a solution...
--
dim
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